Rebound and attachment involving single bubble and particle in the separation of plastics by froth flotation

Bubble-particle interaction is critical to the separation of particles by flotation which can be used in plastic recycling. The two particular processes of the interaction (rebound and attachment) are examined visually using high-speed photography in a laboratory scale flotation column. The effects of surfactant (concentration and type) and plastic material on these two stages are also studied quantitatively. The considered surfactants are Tea Saponin, SDBS and CTMAB, while the plastic materials are polyethylene, polypropylene and Teflon. A simple model of bubble attachment time is developed to analyse and interpret the experimental data. The results show that the presence of surfactant significantly affects the rebound process of a gas bubble, while the type of surfactant and plastic material seem to have slight effect. The bubble attachment process is a strong function of the surfactant and plastic material, which can be associated with the changing of bubble size and its hydrodynamic fluid resistance, contact angle on solid surface, as well as surface tension and viscosity of the solution. Such results are helpful for evaluation and analysis of the plastic flotation process, especially for the selection of reagents and objects at an early stage of design. (c) 2015 Elsevier B.V. All rights reserved.